Cleaning liquid, and method of cleaning substrate provided with metal resist

ABSTRACT

A cleaning liquid usable for cleaning a substrate provided with a metal resist, the cleaning liquid including a solvent, an organic acid, and a compound (A) represented by general formula (a-1) shown below (in the formula, Ra 1  and Ra 2  each independently represents an alkyl group having 1 to 3 carbon atoms).

TECHNICAL FIELD

The present invention relates to a cleaning liquid, and a method ofcleaning a substrate provided with a metal resist.

Priority is claimed on Japanese Patent Application No. 2019-075725,filed Apr. 11, 2019, the entire content of which is incorporated hereinby reference.

DESCRIPTION OF RELATED ART

The processing of semiconductor circuits and devices has involved thecontinued shrinkage of critical dimensions over each generation. Asthese dimensions shrink, new materials and methods are required to meetthe demands of processing and patterning smaller features.

Patterning generally involves selective exposure of a thin layer of aradiation sensitive material (resist) to form a pattern that is thentransferred into subsequent layers or functional materials. There hasbeen proposed a metal resist suitable for providing good absorption forEUV (extreme ultraviolet light) and EB (electron beam) while providingvery high etching contrast (for example, see Patent Literature 1).

In patterning using such a metal resist, a ligand coordinated to a metalperoxide in the metal resist is decomposed by exposure, hydrolysis andcondensation proceed, a metal oxide is formed, and the resist becomeshardly soluble in a developer. Subsequently, by developing the resist, apattern exhibiting a high etching resistance may be formed.

However, in patterning using a metal resist, when a metal resist isapplied to a substrate, clusters of metal peroxide may be bonded to thesurface of a substrate such as a silicon wafer, and residues may begenerated.

In order to remove such residues, it has been proposed to use a cleaningliquid containing an organic solvent and a carboxylic acid (for example,see Patent Literature 2).

DOCUMENTS OF RELATED ART Patent Literature

[Patent Literature 1] U.S. Pat. No. 9,176,377

[Patent Literature 2] WO2018/031896

SUMMARY OF THE INVENTION

However, a cleaning liquid containing an organic solvent and acarboxylic acid as described in Patent Literature 2 has room forimprovement in metal removability.

The present invention takes the above circumstances into consideration,with an object of providing a cleaning liquid usable for cleaning asubstrate provided with a metal resist which exhibits improved metalremovability, and a method of cleaning a substrate provided with a metalresist.

For solving the above-mentioned problems, the present invention employsthe following aspects.

A first aspect of the present invention is a cleaning liquid usable forcleaning a substrate provided with a metal resist, the cleaning liquidincluding a solvent, an organic acid, and a compound (A) represented bygeneral formula (a-1) shown below.

In the formula, Ra¹ and Ra² each independently represents an alkyl grouphaving 1 to 3 carbon atoms.

A second aspect of the present invention is a method of cleaning asubstrate provided with a metal resist, the method including: cleaning asubstrate provided with a metal resist using the cleaning liquid of thefirst aspect.

According to the present invention, there are provided a cleaning liquidusable for cleaning a substrate provided with a metal resist whichexhibits improved metal removability, and a method of cleaning asubstrate provided with a metal resist.

DETAILED DESCRIPTION OF THE INVENTION

(Cleaning Liquid)

The cleaning liquid according to the first aspect of the presentinvention includes a solvent, an organic acid, and a compound (A)represented by general formula (a-1). The cleaning liquid according tothe present embodiment is used for cleaning a substrate provided with ametal resist.

<Solvent>

The solvent is not particularly limited, and examples thereof includewater and an organic solvent.

Examples of the organic solvent include glycol ethers and estersthereof, such as propylene glycol methyl ether (PGME), propylene glycolmethyl ethyl acetate (PGMEA), propylene glycol butyl ether (PGBE), andethylene glycol methyl ether; alcohols, such as ethanol, propanol,isopropyl alcohol, and isobutyl alcohol, hexanol, ethylene glycol andpropylene glycol; cyclic esters such as y-butyrolactone; esters such asn-butyl acetate and ethyl acetate; ketones such as 2-heptanone; liquidcyclic carbonates such as propylene carbonate and butylene carbonate;and cyclic sulfones such as sulfolane.

Among these examples, the solvent is preferably an organic solventhaving no hydroxyl group, more preferably glycol ether or ester thereofor ketone, and still more preferably propylene glycol methyl ether(PGME), propylene glycol methyl ethyl acetate (PGMEA) or 2-heptanone,and most preferably, propylene glycol methyl ethyl acetate (PGMEA).

By using an organic solvent having no hydroxyl group as the solvent, itbecomes easier to suppress the esterification reaction of the acid(formic acid) in the cleaning liquid, the temporal stability of thecleaning liquid may be reliably improved.

In the present embodiment, as the solvent, one kind of solvent may beused, or a mixed solvent containing two or more kinds of solvents may beused.

In the cleaning liquid of the present embodiment, the amount of thesolvent with respect to the total mass of the cleaning liquid ispreferably 30 to 89.9% by mass, more preferably 40 to 84.7% by mass,still more preferably 47.5 to 79.5% by mass, and most preferably 53 to69.3% by mass.

<Organic Acid>

The organic acid is not particularly limited, and examples thereofinclude carboxylic acids such as formic acid, acetic acid, citric acid,oxalic acid, 2-nitrophenylacetic acid, 2-ethylhexanoic acid anddodecanoic acid; sugar acids such as ascorbic acid, tartaric acid andglucuronic acid; sulfonic acids such as benzenesulfonic acid andp-toluenesulfonic acid; phosphoric acid esters such as bis(2-ethylhexyl) phosphoric acid; and phosphoric acid.

Among these examples, as the organic acid, formic acid, acetic acid oroxalic acid is preferable, and formic acid is more preferable.

In the cleaning liquid of the present embodiment, the amount of theorganic acid with respect to the total mass of the cleaning liquid ispreferably 10 to 60% by mass, more preferably 15 to 55% by mass, stillmore preferably 20 to 50% by mass, and most preferably 30 to 45% bymass.

When the amount of the organic acid is within the above-mentionedpreferable range, the metal removability of the cleaning liquid may bereliably improved.

<Compound (A)>

The compound (A) is represented by general formula (a-1) shown below,and functions as a chelating agent.

In the formula, Ra¹ and Ra² each independently represents an alkyl grouphaving 1 to 3 carbon atoms.

In formula (a-1), examples of the alkyl group having 1 to 3 carbon atomsrepresented by Ra¹ and Ra² include a methyl group, an ethyl group, apropyl group and an isopropyl group.

In the cleaning liquid of the present embodiment, the amount of thecompound (A) with respect to the total mass of the cleaning liquid ispreferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, stillmore preferably 0.5 to 2.5% by mass, and most preferably 0.7 to 2% bymass.

When the amount of the compound (A) is within the above-mentionedpreferable range, the metal removability of the cleaning liquid may bereliably improved by the chelating effect of the compound (A).

<Other Components>

The cleaning liquid of the present embodiment may contain, in additionto the above components, other components as long as the effects of thepresent invention are not impaired.

Examples of the other component include an inorganic hydrofluoric acid,a tetraalkylammonium compound, and a surfactant.

Examples of the inorganic hydrofluoric acid include hexafluorosilicicacid, hexafluorophosphoric acid, and fluoroboric acid.

Examples of the tetraalkylammonium compound include tetramethylammoniumfluoride, tetrabutylammonium fluoride, and tetrabutylammoniumfluorosilicate.

Examples of the surfactant include a polyalkylene oxide alkyl phenylether surfactant, a polyalkylene oxide alkyl ether surfactant, a blockpolymer surfactant composed of polyethylene oxide and polypropyleneoxide, a polyoxyalkylene distyrenated phenyl ether surfactant,polyalkylene tribenzyl phenyl ether surfactants, and acetylenepolyalkylene oxide surfactants.

As the additive, one kind of additive may be used, or two or more kindsof additives may be used in combination.

In the cleaning liquid of the present embodiment, the amount of theadditive with respect to the total mass of the cleaning liquid ispreferably 0 to 10% by mass.

The pH of the cleaning liquid according to the present embodiment in a20% aqueous solution is preferably 1.9 or less, more preferably 1.8 orless, and still more preferably 1.7 or less.

When the pH of the cleaning liquid in a 20% aqueous solution is withinthe above-mentioned preferable range, the metal removability of thecleaning liquid may be more reliably improved.

When the cleaning liquid according to the present embodiment does notsubstantially contain water, the pH may be measured after diluting withwater to prepare a 20% aqueous solution.

Alternatively, when the cleaning liquid according to the presentembodiment contains a small amount of water, a 20% aqueous solution maybe prepared by adding and diluting a considerable amount of water, andthe pH may be measured.

The pH may be measured using a commercially available pH meter.

<Substrate Provided with Metal Resist>

The cleaning liquid according to the present embodiment is used forcleaning a substrate provided with a metal resist.

The substrate is not particularly limited, and a conventionally knownsubstrate may be used. Examples thereof include a substrate for anelectronic component, and a substrate on which a predetermined wiringpattern is formed. Specific examples of the material of the substrateinclude metals such as silicon wafer, copper, chromium, iron andaluminum; and glass.

The metal resist is not particularly limited, and includes a resistcontaining at least one metal selected from the group consisting of Sn,Hf, Zr, In, Te, Sb, Ni, Co, Ti, W, Ta and Mo.

More specifically, a metal resist and a patterning method described inany of U.S. Pat. No. 9,176,377B2, US2013/0224652, U.S. Pat. No.9,310,684, US2016/0116839, Jiang, Jing; Chakrabarty, Souvik; Yu, Mufei;et al., “Metal Oxide Nanoparticle Photoresists for EUV Patterning”,Journal Of Photopolymer Science And Technology 27(5), 663-6662014, APlatinum-Fullerene Complex for Patterning Metal ContainingNanostructures, D. X. Yang, A. Frommhold, D. S. He, Z. Y. Li, R. E.Palmer, M. A. Lebedeva, T. W. Chamberlain, A. N. Khlobystov, A. P. G.Robinson, Proc SPIEAdvanced Lithography, 2014, US2009/0155546, U.S. Pat.No. 6,566,276 may be used.

Among these examples, a silicon wafer is preferable as the substrate,and a metal resist containing Sn is preferable.

The cleaning liquid according to the present embodiment described abovecontains the compound (A) which functions as a chelating agent.

Therefore, it is presumed that the cleaning liquid according to thepresent embodiment exhibits high metal removability as compared to aconventional cleaning liquid containing a solvent and an organic acid.

(Method of Cleaning Substrate Provided with Metal Resist)

A second aspect of the present invention is a method of cleaning asubstrate provided with a metal resist, the method including: a step ofcleaning a substrate provided with a metal resist using the cleaningliquid of the first aspect (hereafter, this step is sometimes referredto simply as “cleaning step”).

The substrate and the metal resist are the same as defined for thesubstrate and the metal resist described above in relation to thecleaning liquid of the first embodiment.

In the present embodiment, the cleaning step is not particularlylimited, and examples thereof include a known cleaning method in asemiconductor manufacturing process such as edge bead removal and backrinsing.

In the present embodiment, the step of cleaning a substrate providedwith a metal resist preferably includes applying the cleaning liquidaccording to the first aspect along the periphery of the substrate toremove an edge bead on the substrate (hereinafter, this operation issometimes referred to as “edge rinse”).

The edge rinsing method is not particularly limited as long as it is aconventionally known process, and examples thereof include a methoddescribed in WO2018/031896.

The number of times of edge rinsing is not particularly limited, and maybe performed 1 to 20 times. Further, two or more cleaning liquids may beapplied during edge rinsing.

In the edge rinse, the cleaning liquid may be dripped in an amount ofpreferably 0.05 to 50 mL, more preferably 0.075 to 40 mL, and still morepreferably 0.1 to 25 mL.

As another embodiment, in the edge rinse, the cleaning liquid may besprayed at a flow rate of preferably 5 mL/min to 50 mL/min, morepreferably for 1 second to 5 minutes, and still more preferably for 5seconds to 2 minutes.

In order to evaluate metal removability by edge rinsing, it is possibleto inspect for residual metal on the substrate. Suitable approaches thatare commercially available for the evaluation of trace metals generallyinclude inductively coupled plasma mass spectrometry (ICP-MS). Forevaluation of the substrate surface, gas phase decomposition-ICP-MS(VPD-ICP-MS) may be used. By using this technique, residual metal may bedetermined per unit area of the wafer surface along the edge.

In the present embodiment, in the case where the metal resist is aSn-based resist, the amount of residual Sn is preferably 100×10¹⁰atoms/cm² or less, more preferably 90×10¹⁰ atoms/cm² or less, and stillmore preferably 80×10¹⁰ atoms/cm² or less.

According to the method of cleaning a substrate provided with a metalresist according to the embodiment described above, since the substrateprovided with a metal resist is cleaned using a cleaning liquidcontaining a solvent, an organic acid, and a compound (A), good metalremovability may be exhibited.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

<Preparation of Cleaning Liquid>

Example 1, Comparative Example 1

The components shown in Table 1 were mixed together to obtain eachcleaning liquid.

TABLE 1 Che- Amount of lating pH residual Sn Solvent Acid agent (20%aq.) [×10¹⁰ atom/cm²] Comparative PGMEA Formic — 1.66 102 Example 1 [60]acid [40] Example 1 PGMEA Formic (A)-1 1.67 32 [59] acid [1] [40]

In Table 1, the reference characters indicate the following. The valuesin brackets [ ] indicate the amount (in terms of parts by mass) of thecomponent added. The pH is a value measured by diluting the cleaningliquid of each example with water to prepare a 20% aqueous solution.

PGMEA: Propylene glycol methyl ethyl acetate

(A)-1: Acetylacetone

<Evaluation of Sn Removability>

On a 6-inch Si wafer, 1.5 mL of an organometallic tin oxyhydroxideresist (manufactured by Impria) was applied, and a Sn resist film wasformed by spin coating.

Next, 5 mL of the cleaning liquid of each example was applied to the Siwafer on which the Sn resist film was formed, and the wafer was rotatedat 1,500 rpm for 45 seconds until the wafer was dried. After repeatingthis cleaning operation 5 times, 5 mL of a mixed solution of propyleneglycol methyl ether (PGME) and propylene glycol methyl ethyl acetate(PGMEA) in a mass ratio of 50% was applied, and the wafer was dried at1,500 rpm for 45 seconds until the wafer was dried.

Next, the amount of residual Sn (×10¹⁰ atom/cm²) was measured byChemTrace (registered trademark) using gas phasedecomposition-inductively coupled plasma-mass spectrometry (VPD-ICP-MS).The results are shown in Table 1.

From the results shown in Table 1, it was confirmed that the cleaningliquid of Example 1 had a smaller amount of residual Sn than thecleaning liquid of Comparative Example 1, and had good metalremovability.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A metal resist cleaning liquid comprising: asolvent, an organic acid, and a compound (A) represented by generalformula (a-1) shown below:

wherein Ra¹ and Ra² each independently represents an alkyl group having1 to 3 carbon atoms.
 2. The metal resist cleaning liquid according toclaim 1, wherein the solvent is an organic solvent having no hydroxygroup.
 3. The metal resist cleaning liquid according to claim 1, whereinthe amount of the compound (A) based on the total mass of the cleaningliquid is 0.1 to 10% by mass.
 4. The metal resist cleaning liquidaccording to claim 2, wherein the amount of the compound (A) based onthe total mass of the cleaning liquid is 0.1 to 10% by mass.
 5. Themetal resist cleaning liquid according to claim 1, wherein the amount ofthe organic solvent based on the total mass of the cleaning liquid is 10to 60% by mass.
 6. The metal resist cleaning liquid according to claim2, wherein the amount of the organic solvent based on the total mass ofthe cleaning liquid is 10 to 60% by mass.
 7. The metal resist cleaningliquid according to claim 3, wherein the amount of the organic solventbased on the total mass of the cleaning liquid is 10 to 60% by mass. 8.A method of cleaning a substrate provided with a metal resist, themethod comprising cleaning a substrate provided with a metal resistusing the metal resist cleaning liquid of claim
 1. 9. The methodaccording to claim 8, which comprises applying the metal resist cleaningliquid of claim 1 along the periphery of the substrate to remove an edgebead on the substrate.